Method of thermal pretreatment of volatile coals for carbonizing and coking processes



March 5, 1935. Q w s E METHOD OF THERMAL PRETREATMENT OF VOLATILE GOALS FOR CARBONIZING AND COKING PROCESSES Filed April 25, 1950 Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE Clarence B. Wisner, Orange, N. J., assignor to Coal Process Corporation, Dover, Del., a corporation of Delaware Application April 25, 1930, Serial No. 447,289

1 Claim.

The invention relates to the oxy-thermal pretreatment of volatile coals, which is set forth and described in my United States Patents No. 1,490,357, dated April 15, 1924, and No. 1,756,896, dated April 29, 1930; and the improvement consists in bringing the oxidizing medium into more intimate contact with the hydrocarbons of the finely divided coal under treatment by pressure to cause turbulence, and in restricting the introduction of the oxidizing medium to that part of the heating container in which the surface moisture of the coal has been eliminated and the temperature thereof brought up to approximately 350 F.

By the use of the improved method, and the apparatus which may be employed for carrying it out, the required reaction between the coal and oxygen is quickened, the time of treatment materially shortened, and the capacity of the apparatus is largely increased.

In the United States patents referred to, I have described an oxy-thermal pretreatment step which Iterm thermodizing, in which oxygen is brought into contact with volatile coals during a preliminary heating while the coal is being tumbled through a rotating cylindric container; in accordance with which there have been many thousands of tons of coal successfully processed by the method described therein, and in so doing, I have discovered the improvements which are the subject matter of this specification.

It is well known to coal chemists that when finely crushed volatile coal is heated within a closed retort to 350 F., there occurs the first thermo-chemical reaction exothermic in nature, in which water vapor with small amounts of carbon monoxide and carbon dioxide are driven off, and I have found that this reaction continues active until a temperature approaching 450 F. is reached; during which temperature range the coal will give off water vapor and gas, and at which latter temperature the reaction is over and no more volatile will be given off until pyrolysis begins.

And I have discovered that it is within this definite temperature range that the coal is in a nascent condition as regards oxygen, that is, it is free to be rapidly modified and conditioned for coking in ovens and carbonizing in retorts, for stopping sticking to container walls and controlling expansion during the softening period of carbonization, for producing a denser and stronger product, and for shortening the process cycle, thereby contributing a new step to carbonization technol y.

Without thermodizing the volatile coal, it would be impossible to carry out the carbonization step of making the automatically formed coal balls, which are recognized as the highest type of domestic fuel, in the manner set forth in my said Patent No. 1,756,896.

The time of the thermodizing step will vary with the different types of volatile coal and the purpose for which the coal is to be used in its modified and conditioned form, and for modifying and conditioning volatile coals the time required may be as little as 10 to 15 minutes in high oxygen coals of non-coking type, while medium oxygen coals may require 15 to 30 minutes, and the lower oxygen types of the older geological ages may require up to 45 minutes; the time being controlled by the elevation of the feed end of the retort and the speed of rotation.

The oxidizing fiuid will also vary according to the oxygen-hydrogen ratio shown by ultimate analysis, from 0 cubic feet to 2000 cubic feet, per ton of coal, that is, from a nominally inert to a strongly oxidizing atmosphere.

Until the free moisture is driven off of the coal and its temperature raised to 350 F., the reaction between oxygen and hydrocarbons is very slight, whereas from this temperature to 450 F. it is very active; the coal being in a preferred condition to be modified by thermodizing, which is carheat in the coal speeding up capacity in the carbonization step. However, in the thermodizing step, the coal must never be heated high enough to soften it or start hydrocarbon vapor.

It is known that if coking coals are stored in air long enough they will entirely lose their coking quality, and in this connection it has been proposed to oxidize coals for carbonization at or below steam forming temperature; but here again time is the limiting factor, the reactions being too slow and unstable to be worthwhile.

The improved process may be carried out by the apparatus illustrated, more or less diagrammatically, in the accompanying drawing forming part hereof, in which- Figure 1 is a side elevation of a thermodizing and carbonizing apparatus, showing the thermodizing container in longitudinal section;

Fig. 2, a discharge end view of the thermodizing retort; 1 I

Fig. 3,'a' transverse section of the same as on line 33, Figs. 1 and 4; and

Fig. 4, a fragmentary longitudinal section as on line 44, Fig. 3.

Similar numerals refer to similar parts throughout the drawing. The thermodizing retort may incude an outer cylindric shell 5, and an inner cylindric shell 6 spaced within the outer shell to form an annular flue 7 between the shells, through which heating ases may be impelled, one way or the other, for heating the inner shell or coal container 6.

The retort may have a diameter of some eight feet, and a length of some one-hundred fifty feet, andthe cylindric shells are mounted for rotation upon-their. axis, as by the annular tracks 8 riding on rollers 9; and the same are closed on the coal inlet and discharge ends by the stationary heads 10 and 10a.

il'hetoxidizing medium may be carried into the retort byithe axial pipe 11 extending through the packing gland 12 in the stationary discharge head 10a, into-and through some two-thirds of the length of the coal container; wherein it may be supported by bearings 13 formed in spiders 14 secured. within the coal container shell at the ends of the central one-third portion of the shell. The forward end of the pipe ll may be closed by a cap-15, and depending branch pipes 16 lead downward from the main pipe 11 at the inner sides of the bearings 13, so as to communicate with and -support the pendent pipe 1'7 which extendsparallel with the main pipe, longitudinally throughout the central third of the coal container, immediately above the location of the coal therein during the operation of the retort, as well shown in Fig. 3.

- The pendent pipe 17 is provided with a series ofapertures 18, which are directed toward the surface of the coal in the container, and means as'a centrifugal fan or blower 19 may communicate with the main pipe for impelling a flow of 1 air or other oxidizing agent under pressure into the container.

:-When air is used as the oxidizing medium, it is preferably impelled under pressure into the .pipes so that when discharged in jets through the-apertures in the pendent pipe against the finely divided coal, as it tumbles in the rotatin container, it will create considerable turbulence between the oxygen of the air and the hydrocarbons of the coal, which results in a very rapid conditioning of the coal essential to the improved process of thermodizing.

The main pipe for an eight foot diameter retort one hundred fifty feet long may be eight inches in diameter, more or less, to meet the needs of the particular coal being treated, and the cross area of this pipe will be somewhat larger than the combined openings of the apertures through which the air is discharged against the coal, thus forming an equalizing container, and bringing the temperature of the air near to that of the coal before it is discharged against it.

The air which is discharged in jets from the apertures of the pendent pipe, will fill the container at a reduced pressure, still offering a more or less modifying and conditioning atmosphere: and may be withdrawn through an exit opening 20 from the coal intake end of the container by an induced draft at minus pressure.

In the operation of the apparatus, by the time the raw coal has tumbled through the first third of the length of the container, all of the free moisture will have been driven ofl. and its temperature brought up to substantially 350 F., and while traveling through the central third of the container, it will be subject to the oxidizing medium driven against it, to create a turbulence between the oxygen of the air and the hydrocarbons in the coal, while the temperature is being increased up to 450 F., at which time the thermodizing treatment ofthe coal will be substantially completed; after which the temperature of the coal may be maintained at 450 F., without. the addition of any more air, throughout the remaining last third of the container, whence the coal is discharged into the carbonizing retort 21, which may be located below the thermodizing retort.

I claim:

The method of thermodizing or pretreating volatile coal for carbonizing and coking processes, which comprises heating finely divided coal to at least 350 F., while tumbling it in a closed container to eliminate surface moisture therefrom, then discharging jets of an oxidizing medium under pressure against the tumbling coal for not exceeding 45 minutes to create a turbulence between the oxidizing medium and the hydrocar bons of the coal while heating it to between 350 F. and 450 F., to modify and'improve the coal for coking.

CLARENCE B. WISNER. 

